The present invention relates to a method of manufacturing a porous ceramic structure and, in particular, to a method of manufacturing a ceramic structure in which a ceramic structure having a high porosity can be obtained by mixing a prefoamed resin foam in a ceramics raw material without using a large amount of flammable powder.
Conventionally, there has been known a method of manufacturing a porous ceramic structure in which flammable powders of carbon, wheat flour, resins, and the like are mixed with a ceramics raw material, and the mixture is formed into a formed body which is then fired while the flammable powder material is burned out. According to this manufacturing method, however, there has been a problem that cracking occurs during firing when a large amount of flammable powder is mixed in a ceramics raw material.
In Japanese Patent Laid-Open No. 9-77573, there is described a method of manufacturing a porous cordierite honeycomb structure in which there is used an organic foaming agent capable of foaming at 100xc2x0 C. or below. According to this method, however, there have been problems that heating is needed for the organic foaming agent to foam, that a formed body is deformed when the organic foaming agent foams, that no pores are formed when such a high viscosity material as allowing extrusion is used, and the like.
Accordingly, the present invention has been developed in view of the above described known problems, and an object of the present invention is to provide a method of manufacturing a porous ceramic structure in which a ceramic structure having a high porosity can be obtained without using a large amount of flammable powder.
That is, according to the present invention, there is provided a method of manufacturing a ceramic structure, characterized by mixing a ceramics raw material, a prefoamed resin foam, and a forming aid if needed to prepare a mixture, and forming the mixture into a formed body, and then firing the formed body to obtain a porous ceramic structure.
In addition, according to the present invention, there is also provided a method of manufacturing a ceramic structure, characterized by mixing a ceramics raw material, a prefoamed resin foam, and a plasticizer to prepare a puddle, then forming the puddle into a formed body by extrusion, and subsequently firing the formed body to obtain a porous ceramic structure.
In the present invention, an obtained ceramic structure is preferably a honeycomb structure, which in particular can form a honeycomb filter, as a ceramic structure, having a plurality of through-holes provided with openings on the end surface of the exhaust gas inflow side and the end surface of the exhaust gas outflow side, the plurality of through-holes being plugged alternately on either of both end surfaces.
In addition, a ceramic structure is preferably composed of, as the main components, cordierite, silicon carbide (SiC), and/or silicon carbide (SiC) and metallic silicon (Si).
In the present invention, as for the hardness of a puddle, the puddle is preferably formed in such a way that a mass of the puddle is formed into a solid circular cylinder of 25 mmxcfx86xc3x9730 mm (length) by means of a vacuum pugmill, and the apparent Young""s modulus of the cylinder as measured under a compression rate of 1 mm/s is 3.0 MPa or below, since the resin foam is not crushed so that the pores can be formed as desired. When the apparent Young""s modulus is smaller than 1.5 MPa, no good formed body can be obtained owing to the increased deformation caused by its own weight during forming.
In addition, in the present invention, when a large diameter formed body is desired, a mass of puddle preferably undergoes a downward and vertical extrusion.
In the present invention, the addition amount of a resin foam is preferably 0.5 to 10 wt %, and more preferably 1 to 5 wt %. Furthermore, the average diameter of the resin foam is preferably 2 to 200 xcexcm, and the shell wall thickness of the resin foam is preferably 0.01 to 1.0 xcexcm.